The Mubang 9KF—8042 baler for square straw bale was chosen as research object. 3-D assemble model of D-knotter and its ancillary mechanisms were firstly built up by using SolidWorks software, and imported to ADAMS software for its kinematics simulation and time series analysis of enlacing and knotting process, including sending rope, pushing rope, hanging rope, holding rope, winding rope, biting rope, cutting rope and threading off knot. Knotting principle of D-knotter was revealed. Motion test of the physical prototype showed that reverse designed model of D-knotter and its ancillary mechanisms were accurate, and the results of kinematics simulation recurred the predetermined motion processes of enlacing and knotting requirement correctly. According to the results of kinematics simulation, coupling relationship of motion time series of each functional component was determined.